The present invention relates to a fuel injection system for an engine of a motor vehicle and, in particular, a fuel injection system which includes a single or twin valve type fuel injection arrangement in which the respective intake manifold of the cylinders of the engine are integrated and a fuel injection valve is installed at the point of integration for supplying the fuel.
A single valve type fuel injection system for a motor vehicle engine is a system wherein one fuel injection valve is provided at a branching position of an intake manifold so as to timely supply fuel to each cylinder of the engine. An advantage of a single valve type fuel injection system resides in the fact that it enables a reduction of the number of fuel injection valves required; however, a disadvantage of the single valve type fuel injection system resides in the fact that it is extremely difficult to provide a uniform air stream in the manifold as the number of cylinders increase. Consequently, there is a deterioration in the distribution characteristics of the fuel supplied to each cylinder.
Various proposals have been made to improve the distribution characteristics of the fuel supply and, for example, in Japanese Patent Publication No. 11211/1895, a plurality of cylinders are grouped into odd numbered cylinders and even numbered cylinders, with an intake manifold of each cylinder group being provided with a throttle valve and a fuel injection valve so as to improve the distribution characteristic of the fuel injection valve system.
It has also been determined that a deterioration of the distribution characteristics of the fuel supplied in a single or twin valve type fuel injection system is caused not only by the increase in the number of cylinders of the engine but also by turbulence in the intake air due to a change in velocity occurring when the air passes through the throttle valve and, consequently, to avoid any adverse effects, it is necessary to take measures so as to improve the conditions of the intake air.
The aim underlying the present invention essentially resides in providing a single or twin type fuel injection system which improves the distribution characteristics of the fuel mixture supplied to each cylinder by a method in which the turbulence of an intake air stream, occurring when the stream passes through the throttle valve, is eliminated by regulating the air stream.
More particularly, in accordance with advantageous features of the present invention, an intake manifold of an internal combustion engine having a plurality of cylinders performing the same stroke without overlapping is provided with a fuel injection valve which is positioned on an upstream side of a branching position of the intake manifold and which is adapted to supply fuel to each cylinder. A throttle valve is disposed in an intake air passage on an upstream side of the fuel injection valve with a bent or curved passage member being provided for regulating intake air passing through the air intake passage. The bent or curved member is disposed between the throttle valve and the injection body which accommodates the fuel injection valve so as to improve the air-fuel mixture distribution characteristics of the fuel injection system.
In accordance with the present invention, the intake air stream, when it becomes turbulent as it passes through the throttle valve, is regulated by the bent or curved passage member on the downstream side of the throttle valve and then flows into the injection body. The intake air is mixed therein with the injected fuel to be formed into an appropriate mixture, and the uniform mixture is then distributed and supplied alternately and sequentially to each cylinder by virtue of the regulation effects of the bent or curved passage member.
In accordance with further features of the present invention, the bent or curved passage member is positioned in such a manner that the inner wall surface of said bent or curved passage member which is located at the side of a bending portion having the smallest radius of curvature and the inner wall portion of said bent or curved passage member which is located at the side of the bending portion having the largest radius of curvature are respectively opposed to a portion of said throttle valve which is located on the upstream side and a portion of said throttle valve which is located on the downstream side.
Additionally, in accordance with still further features of the present invention, the single or twin valve type fuel injection system of the present invention is provided with two separate barrels on a downstream side of the throttle valve, with each of the barrels containing or accommodating a fuel injection valve.
Advantageously, the curved passage member includes a skirt means and an outlet thereof which is arranged in such a manner so as to cover the two barrels.
The bent or curved passage member of the present invention is constructed whereby the steamline of air passing through the intake air passage is bent by an angle of 90.degree..
These and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings which show, for the purposes of illustration only, several embodiments in accordance with the present invention.